The use of a single mirror for directing a source of energy such as light beam to or from an optical system such as a detector array is employed for example in video disk players. Canadian Pat. No. 1,089,267 issued Nov. 11, 1980 to Uneki et al discloses one typical system of incorporating a mirror that is wobbled (pivoted on two mutually perpendicular axes) around a centre point by means of two pair of controllable electromagnetic devices so that the precise angular position of the mirror around both axes is controllably adjustable and is therefore known. A similar device is disclosed in U.S. Pat. No. 4,021,096 issued May 3, 1977 to Dragt. In these devices it is the tilting of the mirror about the mutually perpendicular axes that directs the light in the proper direction, the two mutually perpendicular axes are fixed so that there can be no rotation of one of the axes with the other axis.
It is known to rotate a mirror in a scanning system as disclosed for example in U.S. Pat. No. 4,039,246 issued Aug. 2, 1977 to Voigt or U.S. Pat. No. 4,427,878 issued Jan. 24, 1984 to Buchtel which utilize such systems in an optical scanning apparatus for missile seekers. In both of these systems a pair of mirrors rotating on a common axis are used. These mirrors are able to scan a rosette pattern in the field of view.
The above referred to U.S. Pat. No. 4,039,246 of Voigt rotates a secondary mirror around an axis and pivots this secondary mirror on an axis perpendicular to the rotational axis to generate the rosette pattern.
With robotic manipulators the position of the load or a selected point on the robot arm is difficult to determine by standard kinematic relationships alone. When loading on the arm causes distortion of arm segments (eg. bending of an arm segment) such distortions are not accurately predictable and these kinematic relationships do not accurately determine the position of the arm. Also in cases of arms with a multiplicity of links or arm segments excessive amounts of computing time may be required for end point determination using kinematic relationships. Thus some form of direct determination of end point position is desirable particularly to provide feedback to be used in an adaptive control application to correct errors. One way to monitor is to use a video camera configured to view the entire range of movement of the manipulator arm. The disadvantage of using such a system, however, is that the detecting computer would be required to analyze the manipulator's total work area to determine the location of the end point.
Commercially available mirror scanning systems normally have a small scanning range (a viewing range of less than 40 degrees) and employ two mirrors much in the manner of the two mirror systems used in the missile seeker above described in relation to U.S. Pat. Nos. 4,039,246 and 4,427,878.